I started with an old window we found beside a dumpster. Cleaned it up and broke out some of the window panes at the bottom.(Covered both under and over the pane with newspaper and then struck it with a hammer.)
I found some sheet metal already cut-to-size at my local Lowe's and picked up a couple.
For my center pane, I wanted to use some chalkboard...so I used what I had and cut up a shipping box and some chalkboard vinyl.
I had some of the box still poking through- I wasn't completely straight with my application. Whoops. I just used a black Sharpie marker to fill in, just-in-case.
We put the new panels into the window- they were snug enough we didn't need to use any other materials to secure them (lucky us).
We secured it in our entryway above an old hutch I've been using as a table of sorts.